System for variable-speed operation of alternating-current motors.



No. s14,ss0. PATENTED MAR. 6, 1906. B. G. LAMME. SYSTEM FOR VARIABLESPEED OPERATION OF ALTERNATING CURRENT MOTORS.

APPLICATION FILED our. 8. 1964.

5 I3 /7 I6 w WITNESSES: gVENTOR v ATTO'RNEY speeds by varying BENJAMIN(l. LAMME, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC& M PORATlON OF PENNSYLVANIA.

ANUFACIUKING COMPANY, A COR-- SYSTEM FOR VARIABLE-SPEED OPERATlON OFALTERNATING-CURRENT MOTORS.

Specification of Letters Patent.

tatented March 6, 1906.

Application filed October 8, 1904. Serial No. 227,704.

1'0 all whom-it may concern."

Be it known that I, BENJAMIN G. LAMM'E, a citizen of the United States,and a resident of Pittsburg, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in Svstems forV ariable-Speed Operation of Alternating-Cur rent Motors, of which thefollowing is a specification.

My invention relates to alternating-cur rent motors; and it has for itsobject to pro vide a simple means for operating such motors eliicientlyat variable speeds.

For many classes of work it is very desir able to employ motors whichmay be oper ated at low speeds, as well as at much higher speeds, with aconsumption of I and variable power that is substantially proportionalto the speed. I propose to utilize inductionmotors for'such service andto vary the motor the voltage and the frequency of alternations of thecurrents sup-- plied thereto.

A suitable method of varying the frer uency of an alternating current isset forth in atent No. 682,943, granted to tho lVestinghouse Electric&'l\ l anufacturing Company September 17, 1901, upon an applicationfiled by me which consists in supplying alternating cur rents of a givenfrequency through brushes and collector-rings to the armaturenvinding ofa rotary converter the ficld-magnet of which is unprovided with.111agnetizing-coils and driving the armature at such. speed bctween zeroand synchronism as will insure the supply of currents of the desired frouency to the coinmutatordeads. Since the re uency-changing ap )aratusmay he of suc 1 construction as will permit of its being operated atrelatively high speeds, it need not be large or costly as compared withthe motor which it is intended to control, and consequently its usepermits of economical speed-control of the simplest form of drivingmotor.

In. ordinary operation if the voltage supplied to a motor is not variedapproximately in proportion to the variations in the frequency ofalfsu'natirms of the current the magnetic-flux density in the stator orfield magnet of the motor will rise as the frequency of alternations isdecreased.

} V This is a conditron tending toward very large torques at l l l l Ilow speeds, but represents also a condition of high wattless-currentinput to the motor at the lower speeds, and therefore low-power factors.Such a frequency-elm.nging device as. is described in Patent No. 682,943has the characteristic of changing the frequency of alternations of thecurrent without changing the voltage ratio-that is, with a given vol.-tage applied at the collector-ring end of the machine the voltagedelivered at the com.- mutator end will be practically constant, andtherefore independent of the frequency of alternations of the current.

According to my present invention a means for varying the voltage-suclnfor example, as a transformer with variahie-voltage ratio, or aregulator having relatively adjustable primary and secondary members--isemployed between the main su nily-circuit and the frequency-elmuger orbetween the frequency-changer and the inductionmiotor.

As illustrated in the single figure of the accompanying drawing,alternating-current enorgy supplied from a suitable source 1 to anautotransformcr :2, one terminal of which is connected to a brush 3,bearing upon a collcctor-ring 4 at one end of a frcquencya'hanger 5,which ,is of a type of construction such as has been hereinbeforedescribml.

The autoiranstormer-wimling :2 is suitably subdivided by means of leads6, which are respectively connect-ed to contactd'crminals 7, withwhich apivoted arn'i S is adapted to engage the arm 8 being connected to abrush 5'), which bears upon a collector-ring 10 of the frequency changer5. Bearing upon the commutator-0y]indcr 11 at the other end of thearmature of the frequcncv-changor 5 are three brushes 12, which areconnected to the proper points in the priunu v winding 13 of animluction-rnotor .15. I

The autotransfer!ncr-wiiuling 22 may be replaced by a two-windingtransformer one of the windings of which is suitably sululividcd bymeans of leads in a manner similar to that here shown in connection withthe autol runs-- or it may be replaced by a regulator having primary andsecondary windings the ipdurtivc relations of which with. respect toeach olhcr are adjustable. Evidently any other suitable voltagcWa-ryingdevice may be employed. 7

, lVhile I have shown the iirequenryi1haugcr 5 as supplying three-phaseenergy to the induction-motor 15, it is to be understood thatsingle-phase or two-phase ener y or energy of any other desired numberof phases inay be supplied therefrom, what I have shown being designedto illustrate any suitable mechanism for practicing my invention.

If the voltage-regulator is used in connection with a frequency-changeras just described, then the variations in voltage accomplished by thevoltage-regulator may be made to automatically vary the frequencydelivered by the frequency chan ger. To this end I have shown thefrequency-changer 5 as driven by an alternating-current variable-speedmotor 16, the s eed of which varies in proportion to the v tage derivedfrom the autotransformer 2-. The motor is connected in series with thesecondary winding 17 of a transformer 18, the primary winding 19 ofwhich is connected between the terminals of the autotransformer-winding2. One

terminal of the secondary winding 17 is con- I nected to one terminal ofthe primary winding 19, and the free armature-terminal 20 of the motor16 is connected tofthe pivoted arm 8. By means of this arran ement ofconnections a reduction in the V0 tage delivered by the regulatorincreases the voltage supplied to the driving-motor 16, and a reductionin voltage supplied to the frequency-changer causes its speed toincrease, and thus the frequency of alternationsofthe current isreduced. Hence the frequency of alternations of the current delivered tothe induction-motor is made to vary approximately as the voltage isvaried.

One of the principal advantages of my invention lies in the fact thatthe frequencychanger may be a polyphase machine having a rotatingmagnetic field, and consequently its least losses and easiest conditionsas regards commutation occur at or near synchronous speed when it isdelivering its lowest frequency. Such a machine can therefore carry veryheavy loads when delivering currents of low frequency, as the machinehas the least losses and is running at the highest speed.

As the speed of the frequency-changer is decreased until it approacheszero speed, the frequency of the current delivered rises, andconsequently the motor that is operated ,by the energy received from itapproaches its highest speed and lowest torque. Therefore as thefrequency-changer approaches a condition of poorest ventilation andhighest losses its load is diminished, thus tending to compensate forthe poorest conditions of operation.

It will be understood that any-kind or type 7 of translating device theoperation of which may be efficiently controlled by varying the voltageand current alternations of the energy supplied thereto may be'employedand that any desired number of such devices may also be utilized.

I claim as my invention 1. The combination with a source ofalternating-current electrical energy of ap roximately constantfrequency and a trans ating device, of means for varying the voltagefrom said source and separate means for antomatically varying thefrequency of current alternations supplied to said devicein accordancewith the voltage variations.

2. The combination with a source of alternating-current electricalenergy. of ap roXimately constant frequency and a trans ating device,of, means for varying the voltage from said source and separate meansfor automatically varying the frequency of current alternations suppliedto said device in approximately the same ratio.

3. The combination with a source of alternating-current electricalenergy, a dynamo-.

electric frequency-changer having no magnetizing field-coils, and atranslating device supplied from the commutator of saidfrequency-changer, of means for varyin the voltagesupplied to thecollector-rings 0% said frequency-changer and means for driving thefrequency-changer at speeds approximately proportional to the variationsinvolta e.

4. The combination with a source 0 alternating-current electricalenergy, means for changing the frequency of current alternationscomprising'a dynamo-electric machine having; no magnetizing field-coils,and a translating device supplied from the commutator of saidfrequency-chan er,,of means for varying the volta e supp ied to thecollectorrings of said equency-changer and means 'for driving thefrequency-changer armature at variable speeds.

. 5. The combination with a source of alternating-current electricalenergy, a machine for changing the frequency of current alternationscomprising a rotary converter having no magnetizing field-coils, and anarmature which is provided with collector-rings and a commutator, and atranslating device supplied from the commutator of said machine, rrieansfor varying the voltage supplied to the collector-rings of the machineand means for varyin the speed of rotation of the armature of thefrequency-changing machine.

6. The combination with a source of alternating-currentelectrical'energy, a machine forchanging the frequency of currentalternations comprising a rotary converter having no ma netizingfield-coils and an armature which is provided with collector-rings anda.

commutator, and a translating device supplied from the commutator ofsaid machine, of means for varying the voltagesup lied to thecollector-rings of the machine an means for varying the speed ofrotation of the armature of the frequency-changing machine apsaidsource, and se arate means proximately in proportion to the variationsin volt e.

7 The combination with a source of alternating-current electricalenergy, a frequency changer com rising an armature rotatable in amagn'etiza le frame, a winding therefor, collector-rings and acommutator, and a motor supplied with energy from the commutator oflthefrequency-chan er, of means for varying the voltage sup lief rings 0 thefrequency-c anger. v 8. The combination with a source ofalternating-current electricalenergy, a frequencychanger comprising anarmature rotatable in a magnetizable frame, a winding therefor,

collector-rings and. a commutator, and a mo-' tor supplied with energyfrom the commu-' tator of the frequency-chan er, of means for varyin thevoltage supplie -to the collector rings 0 the frequency-changersubstantially in proportion to the changes in frequency of alternationsof the current delivered therefrom.

9. The combination with a. source of alternating-current electricalenergy, means for varying. the frequency of current alternationscomprising a rotary converter having magnetizing field-coils, and atranslating device supplied from the commutator of said rotaryconverter, of means for varyin the voltage supplied to thecollector-rings 0 said rotary converter, and-a driving-motor for saidrotary converter the speed of which is varied approximately in inverseproportion to the variations in voltage of the rotary con verter.

, 10. The combination with a source of alternating-current electricalenergy, means for changing the frequency of currentalternationscomprising a rotary converter having no magnetizin field-coils, and atranslating device supplied from the commutator of said rotaryconverter, of means for varyin the voltage supplied to thecollector-rings 0 said rotary converter, a driving-motor for said rotaryconverter and means for supplying a volta e thereto which is inverselyproportionaF converter.

11. The combination with a source of alter-- nating-current electricalenergy of approximately'constant frequency, and a translating device, ofmeans for varying the voltage from said source, and separate means forvarying the frequency of current alternations supplied to said device.12. The combination with a source of alternating-current electricalenerg of ap roximately constant frequency and a trans ating device, ofmeans for varying the voltage from for automatically varyin the equencyof current alternations supp ied to said device.

13. he combination with a source of alternating-current electricalenergy of approxito the collectorelectric fre uenc -changer an a to thevoltage supplied to the rotary.

rying the frequency of current alternations supplied to said device inapproximately the same ratio.

1 The combination with a source of alternating-current electrical enery, a dynamoelectric freqliliencymhanger an a translating device supp edtherefrom, of driving means for the frequency-changer and means forvarying the speed thereof approximately in proportion to variations into the translating device.

15. The combination witha source of alternating-current electricalenergy, a dynamoelectric fre uenc -changer and a device supp ied terefrom, of a driving-motor for the frequency-changer and means forvarying the speed of the driving-motor approximately in proportion tovariations in the voltage su Iplied to the translating device.

1 6. e combination with a source of alternating-current electrical enera dynamotranslating device supp ied t erefrom, of a'driving-motor forthe frequency-changer and means for varying the voltage supplied to thedriVing-motor approximately in inverse proportion to variations in thevoltage supplied to the translating device. I

17. The combination with a source of alternating-current electrical enery, a dynamoelectric frequency-changer an a translating device suppliedtherefrom, of means for varying the voltage from said source, adriving-.

device the voltage supplied translating 18. The combination with asource of alternating-current electrical ener electric frequency-changeran a translating device supplied therefrom, of means for varying thevolta e from said source, a drivingmotor for sai frequency-changer, anda transformer whereby the speed of the driving-m otor is caused toincrease as the voltage supplied to the translating device is decreased.

1 9. The combination with a source of alternating-current electricalenergy, a dynamoelectric frequency-changer and a device suppliedtherefrom, of ineans 'for varying the voltage from said source, adrivingmotor for said transformer whereby the voltage supplied to thedriving-motors is caused to vary approximately inversely proportional tovariations in the voltage supplied to the translating device.

20. The combination witli a source of alternatmg-current electricalenergy, a dynamoelectric frequency-changer and.- a translating ,adynamotranslating 1 frequency-changer, and a devicesupplied therefrom,of means for vatransformer whereby the speed of the drivrying the voltae from said source, a drivinging-motor is adjusted and the frequency ofr 5 motor for said frequency chan er, and a the current alternationssupplied to the transtransformer whereby the speed 0 the drivlatingdevice is varied in accordance with the ing-rnotor is caused to varyapproximately inversely proportional to the variations in voltagesupplied to the translating device.

21. The combination with a source of altermating-current electricalenergy, a dynamoelectric frequency-changer and a translating devicesupplied therefrom, of means for varying the voltage from said source, adrivingmotor for said frequency changer, and a voltage variations.

In testimony whereof I have hereunto subscribed my name this 29th day ofSeptember, 20

BENJ. G. LAMME.

Witnesses:

O'r'ro S. Sormmnn,

BIRNEY HINES.

